Jean-Claude Bunzli - Near-infrared luminescence of nine-coordinate neodymium complexes with benzimidazole-substituted 8-hydroxyquinolines

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      Publication Details (including relevant citation   information):

      Shavaleev,N.M., Scopelliti,R., Gumy,F., Bunzli,J.C.G.   Inorganic Chemistry 2008 47  (19) 9055-9068

      Abstract: A new class of   benzimidazole-substituted 8-hydroxyquinoline ligands has been   prepared that contain a monoanionic tridentate N, N,   O-coordinating unit. These ligands form charge-neutral lanthanide   complexes of the type [Ln(L-R)(3)] center dot nH(2)O or   [Ln(2)(L2)(3)]center dot nH(2)O (n = 1-3) with early lanthanides   from La-III to Gd-III inclusive. Crystallographic   characterization was carried out for 11 complexes with 6   different ligands. In all of these structures, the lanthanide ion   was found to be nine-coordinated by three ligands arranged in an   "up-up-down" fashion around the metal center. The coordination   environment can be described as a tricapped trigonal prism, with   N atoms of quinoline rings occupying capping positions. Upon   deprotonation of the ligand and complex formation, a new   absorption band appears in the visible range of the spectrum with   a maximum in the range of 466-483 nm and molar absorption   coefficient of (7.2 - 18) x 10(3) M-1 cm(-1). Its origin is   likely to be an intraligand phenolate-to-pyridyl charge transfer   transition centered on the 8-hydroxyquinolate chromophore. Upon   excitation in ligand absorption bands, new Nd-III complexes   display characteristic metal-centered luminescence in the   near-infrared region from 850 to 1450 nm with quantum yields and   lifetimes in solid state at room temperature as high as 0.34% and   1.2 mu s, respectively

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